Within a couple of years Unmanned Aerial Vehicles, UAVs, are predicted to fly in civil aerial territory together with civil aeroplanes and according to civil air traffic rules. This will call for very high requirements of security of the systems of an UAV relative third party, both in the air as well as on the ground. For a third party in the air, anti-collision systems and the likes will be available to secure that the safety is met in the air and similar systems will be available to avoid that the vehicle should collide with the ground. However, trouble arises when propulsion of the vehicle ceases to work, and the vehicle is unable to avoid terminating on the ground.
Today the unmanned aerial vehicles operate entirely in designated areas wherein they are allowed to terminate on the ground. To meet the requirements of security for flying in non-designated areas, civil aerial territories, the vehicle must be able to control that it terminates within allowable areas wherein no danger for third parties exist.
Today, UAVs, either remotely piloted vehicles (RPVs) or semi- or fully autonomous, represent an increasingly important field of aircraft technology. When flying autonomous aerial vehicles it is of utter importance to secure in the route planning that the aerial vehicle will be able to reach an approved termination point. If a failure occurs in the UAV, such as engine failure or the like, the UAV must terminate the flight at an approved termination point having an acceptable terrain. Above all, it is necessary to fully exclude the risk of terminating or crashing the UAV in populated areas. This can be achieved by using termination points, wherein these points are predetermined as acceptable points. It is also important as stated above that the UAV is able to reach one of its termination point and that this is secured.
Safety critical system of an UAV should always determine that no danger is present to a third party. These systems require that the vehicle can fly in a normal manner. If an engine failure occurs in an unmanned vehicle a termination to the ground is inevitable, which means that in order to secure the safety of third parties the vehicle must terminate on a predetermined and safe spot.
Document DE, A1, 3124553 discloses a glide path calculation wherein necessary altitude is computed based on the lift and drag ratio to reach a target area.
Document US, A, U.S. Pat. No. 5,142,480 discloses a method to provide an indication if an aircraft can safely glide to a selected airport and display required data, such as required altitude, a predetermined number of airports etc.
Document US, A1, 20040193334 discloses a method of providing a termination route to a vehicle when an emergency situation occurs. The aircraft follows a termination path towards a termination point with a specific altitude and speed.
To enable safe termination in a non-designated area the following are required:                At least one point or area where safe termination is allowed must exist.        The vehicle must always know which termination point it should transfer to, in order to terminate safely.        The vehicle must always be in a position whereat the vehicle can glide to said point or area.Additionally, safety critical systems, such as positioning systems, control systems must also work in order to enable navigation to the termination point.        
The objective of the present invention is to provide an estimated safe termination operation volume wherein each coordinate in the volume fulfils the requirements to provide a safe glide path to an approved termination point which volume can be used to plan a flight route and a termination route in case of emergency.